1. Field of the Invention
The present invention relates to an image receiving medium for use in combination with a thermal image transfer recording medium for a sublimation-type thermal image transfer recording system, and more particularly to an image receiving medium for use in a sublimation-type image transfer recording system is composed of a support, an intermediate layer containing an isocyanate compound, and a dye-receiving layer containing an active-hydrogen-containing resin, an isocyanate compound and a polyether-modified silicone, which layers are overlaid in this order on the substrate.
2. Discussion of Background
A sublimation-type thermal image transfer recording system is characterized by employing a thermal image transfer recording medium which comprises a dye-transfer layer containing a heat-sublimable dye, and an image receiving medium capable of receiving the dye which is sublimed when the thermal image transfer recording medium is superimposed on the image receiving medium and heated from the back side thereof. Since the above recording system can produce a full-colored hard copy with an excellent halftone, comparable to a color photograph, it is greatly attracting public attention now.
The conventional image receiving medium for use in the above sublimation-type thermal image transfer recording system is constructed in such a fashion that a dye-receiving layer comprising (i) a thermoplastic resin such as a polyester resin, which can be readily dyed with a heat-sublimable dye, and (ii) a releasing agent is formed on a support such as a sheet of synthetic paper. However, that kind of conventional image receiving medium has the shortcoming that the image receiving medium readily fuses when thermal recording is conducted, and sticks to a thermal image transfer recording medium (for example, a color sheet) because of the low heat-resistance of the polyester resin contained in the image-receiving medium.
To solve the above problem, the releasing agent has been incorporated into a dye-receiving layer of the image receiving medium, so that the releasability of the dye-receiving layer of the image receiving medium from the thermal image transfer recording medium can be improved.
When the amount of the aforementioned releasing agent is small, however, a dye-transfer layer of the thermal image transfer recording medium is peeled off a substrate thereof and transferred to the image receiving medium so far as the adhesion strength between the dye-transfer layer and the substrate is not so high.
On the other hand, when the releasing agent is incorporated in the dye-receiving layer of the image receiving medium in a sufficient amount to improve the releasability of the dye-receiving layer of the image receiving medium from the thermal image transfer recording medium, the adhesion between the support and the dye-receiving layer of the image receiving medium is decreased and the dye-receiving layer is peeled off the support and transferred to the thermal image transfer recording medium after thermal recording.
In addition, since the compatibility of the releasing agent with a resin generally contained in the dye-receiving layer of the image receiving medium is not so high, the transparency of the dye-receiving layer becomes low as the amount of the releasing agent is increased. In particular, a transmission-type image receiving medium, for example, an image receiving sheet for an over head projector is required to have a highly transparent dye-receiving layer. In the case of a reflection-type image receiving medium, as a matter of course, the higher the transparency of the dye-receiving layer, the clearer the images recorded thereon.